Method and apparatus for cleaning substrates

ABSTRACT

An ultrasonic vibrating apparatus and an ultrasonic cleaning apparatus capable of permitting ultrasonic cleaning of a wafer to be carried out using an existing cleaning tank and while keeping the object immersed in cleaning liquid. An ultrasonic wave is irradiated to a cleaned object while keeping it immersed in cleaning liquid stored in a cleaning tank formed with an upper opening. A vibrating plate is securely mounted thereon with an ultrasonic transducer through a wave transmission element and arranged so as to close the upper opening of the cleaning tank in a cover-like manner. The vibrating plate is so arranged that a vibrating surface thereof downwardly faces and is immersed in the cleaning liquid.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims priority to Japanese Patent Application No. 206069/2001 filed Jul. 6, 2001, and is also hereby incorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

[0002] This invention relates to techniques for cleaning objects using an ultrasonic vibrating and cleaning apparatus. More particularly, the invention provides an ultrasonic vibrating apparatus for cleaning an object to be cleaned using an ultrasonic wave and an ultrasonic cleaning apparatus having the same incorporated therein. Merely by way of example, the invention can be applied to cleaning semiconductor wafers. But it would be recognized that the invention can also be applied to masks, flat panel, MEMS object, hard disks, optical devices, and the like.

[0003] A semiconductor device such as a semiconductor memory is manufactured by subjecting a semiconductor wafer (hereinafter referred to as wafer) such as a silicon wafer or the like to various kinds of processes or treatments. Manufacturing of the semiconductor device encounters problems such as adhesion of dust thereto or inclusion of dust thereon, thus, it is important to prevent such adhesion or inclusion in the manufacturing. However, it is difficult to avoid adhesion of dust to a surface of a wafer during treatments thereof. In particular, it is difficult or substantially impossible to prevent adhesion of particulate dust as fine as submicrons to a wafer. Thus, prior to respective treatments of a wafer, the wafer is generally subject to cleaning, to thereby reduce adhesion of dust thereto to a predetermined level or below, followed by treatment of the wafer.

[0004] A wafer cleaning apparatus which has been conventionally proposed is in the form of an ultrasonic cleaning apparatus constructed in such a manner as shown in FIG. 5. The conventional ultrasonic cleaning apparatus generally designated at reference numeral 60 in FIG. 5 generally includes a cleaning tank 63 which is filled therein with cleaning liquid 62 heated for cleaning wafers 61 and a cooling tank 65 which is filled therein with cooling water 64. Also, the ultrasonic cleaning apparatus includes an ultrasonic vibrating apparatus. The ultrasonic vibrating apparatus includes either a vibrating plate 66 arranged on a bottom wall of the cooling tank 65 or a vibrating plate (not shown) arranged on a side wall 67 thereof, as well as an ultrasonic transducer 68 fixedly mounted on the vibrating plate by means of an adhesive 69. The ultrasonic transducer 68 is cooled by the cooling water 64. The ultrasonic transducer 68 may be constructed so as to generate an ultrasonic wave having a frequency set within a range of between 200 kHz and 1 MHz. The cleaning liquid 62 overflowing the cleaning tank 63 is guided to an overflow tank 70 and then discharged therefrom.

[0005] When the heated cleaning liquid is not used, the ultrasonic vibrating apparatus may be constructed in such a manner that the cleaning tank is directly fixedly mounted on either a bottom wall thereof or a side wall thereof with the ultrasonic transducer acting as an ultrasonic vibrating device without using the cooling tank 66 shown in FIG. 5. The bottom wall or side wall of the cleaning tank is cooled by the cleaning liquid, to thereby cool the ultrasonic transducer mounted thereon.

[0006] The conventional ultrasonic cleaning apparatus may be realized in the form of a megahertz ultrasonic cleaning apparatus adapted to generate an ultrasonic wave having a frequency within a range of between 850 kHz and 1 MHz, to thereby exhibit a function of satisfactorily removing micro particles of submicrons adhered to wafers therefrom by cleaning. Thus, in the megahertz ultrasonic cleaning apparatus, the ultrasonic transducer is mounted on the side wall or bottom wall of the cooling tank or cleaning tank and SC-1 or pure water is used as the cleaning liquid. An ultrasonic wave having a frequency within the above-described range is irradiated into the cleaning liquid stored in the cleaning tank, so that particulate dust as fine as submicrons adhered to wafers immersed in the cleaning liquid may be removed therefrom utilizing a catalytic acting force due to vibrational acceleration at a large magnitude.

[0007] Another conventional ultrasonic cleaning apparatus is known in the art, which includes an ultrasonic vibrating apparatus constructed so that an ultrasonic vibrating apparatus including an ultrasonic transducer and a wave transmission element coupled to each other is substituted for the ultrasonic transducer 68.

[0008] A further conventional ultrasonic cleaning apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. 94756/1998. The apparatus disclosed is constructed in such a manner that an ultrasonic vibrating apparatus in which an ultrasonic transducer for generating an ultrasonic wave of 500 kHz or more in frequency and a wave transmission element for guiding ultrasonic vibration are coupled to each other is arranged above cleaning liquid and an ultrasonic wave is emitted from the ultrasonic transducer toward the cleaning liquid, to thereby expose wafers arranged below a cleaning liquid vessel in which the cleaning liquid is stored to a shower of the cleaning liquid in a downward direction, resulting in the wafers being cleaned.

[0009] In each of the ultrasonic cleaning apparatus, a size of the cleaning tank or cleaning liquid vessel, a frequency of the ultrasonic transducer, power desired for ultrasonic vibration and the like may be selected as desired so as to ensure cleaning of an object to be cleaned such as liquid crystal or the like as well as a wafer. However, the conventional ultrasonic cleaning apparatus each have one or more disadvantages.

[0010] In the conventional ultrasonic cleaning apparatus in which the ultrasonic vibrating apparatus is mounted on the side wall or bottom wall of the cooling tank or cleaning tank, various kinds of pipings are arranged on the side wall or bottom wall of the cooling tank or cleaning tank or various kinds of units are arranged around the ultrasonic cleaning apparatus. This causes maintenance of the ultrasonic vibrating apparatus mounted on the side wall or bottom wall, replacement thereof and the like to be highly troublesome.

[0011] In the conventional ultrasonic cleaning apparatus in which the ultrasonic vibrating apparatus is arranged above the cleaning liquid, a shower of the cleaning liquid stored in the cleaning liquid vessel is blasted against wafers placed below the vessel to clean it. This often fails to clean the wafer while keeping it immersed in the cleaning liquid.

[0012] Further, it is desirable to carry out megahertz ultrasonic cleaning of wafers using an existing cleaning tank. Unfortunately, such a cleaning apparatus has not been developed in the art.

BRIEF SUMMARY OF THE INVENTION

[0013] According to the present invention, techniques for cleaning objects have been provided. More particularly, the invention provides an ultrasonic vibrating apparatus for cleaning an object to be cleaned using an ultrasonic wave and an ultrasonic cleaning apparatus having the same incorporated therein. Merely by way of example, the invention can be applied to cleaning semiconductor wafers. But it would be recognized that the invention can also be applied to masks, hard disks, flat panel, MEMS object, optical devices, and the like.

[0014] In accordance with one aspect of the present invention, an ultrasonic vibrating apparatus is provided for irradiating an ultrasonic wave to a cleaned object kept immersed in cleaning liquid stored in a cleaning tank formed with an upper opening. The ultrasonic vibrating apparatus includes a vibrating plate for closing the upper opening of the cleaning tank in a lid-like manner and at least one ultrasonic transducer fixedly mounted on the vibrating plate. The vibrating plate is arranged in such a manner that a vibrating surface thereof outwardly faces and is adapted to be immersed in the cleaning liquid stored in the cleaning tank.

[0015] In accordance with this aspect of the present invention, an ultrasonic vibrating apparatus is also provided for irradiating an ultrasonic wave to a cleaned object kept immersed in cleaning liquid stored in a cleaning tank formed with an upper opening. The ultrasonic vibrating apparatus includes a vibrating plate for closing the upper opening of the cleaning tank in a lid-like manner, a wave transmission element, and at least one ultrasonic transducer fixedly mounted on the vibrating plate through the wave transmission element. The vibrating plate is arranged in such a manner that a vibrating surface thereof outwardly faces and is adapted to be immersed in the cleaning liquid stored in the cleaning tank.

[0016] In a preferred embodiment of the present invention, the vibrating plate is provided with a hinge and/or a vertically moving means, to thereby be operatively associated with the cleaning tank.

[0017] In a preferred embodiment of the present invention, a vibrational frequency of the vibrating plate is set to be within a range of between 200 kHz and 5 MHz.

[0018] In a preferred embodiment of the present invention, the vibrating plate is made of a material subjected to a treatment selected from fluoroplastic coating and passivation. The material is selected from the group consisting of stainless steel such as SUS 304, SUS 316 or SUS 316L; tantalum; fused quartz; silicon carbide; and stainless steel of 1 μm (Rmax) in surface roughness.

[0019] In a preferred embodiment of the present invention, a bubble removing means is further arranged on a lower surface of the vibrating plate so as to eject cleaning liquid of a composition identical to that of the cleaning liquid in the cleaning tank to remove bubbles adhering to the lower surface of the vibrating plate therefrom.

[0020] In accordance with another aspect of the present invention, an ultrasonic cleaning apparatus is provided. The ultrasonic cleaning apparatus includes an ultrasonic vibrating apparatus constructed as described above and a cleaning tank formed with an upper opening on which the ultrasonic vibrating apparatus is mounted.

[0021] In accordance with this aspect of the present invention, an ultrasonic cleaning apparatus is also provided. The ultrasonic cleaning apparatus includes an ultrasonic vibrating apparatus constructed as described above, a cleaning tank formed with an upper opening on which the ultrasonic vibrating apparatus is mounted, and a bubble removing means arranged in proximity to the upper opening of the cleaning tank and constructed so as to eject cleaning liquid of a composition identical to that of cleaning liquid stored in the cleaning tank to a lower surface of the vibrating plate of the ultrasonic vibrating apparatus, to thereby remove bubbles adhering to the lower surface of the vibrating plate therefrom.

[0022] There are many benefits that can be achieved over conventional techniques. For example the present ultrasonic vibrating apparatus is capable of permitting ultrasonic cleaning of an object to be cleaned (hereinafter referred to as cleaned object) such as, for example, megahertz ultrasonic cleaning thereof to be effectively carried out using an existing cleaning tank. In some embodiments, the invention can also provide an ultrasonic vibrating apparatus which is capable of cleaning a cleaned object while keeping it immersed in cleaning liquid. Additionally, the invention can provide an ultrasonic vibrating apparatus which is capable of facilitating maintenance and replacement of both ultrasonic vibrating apparatus and components arranged therein. In other embodiments, the invention also provides an ultrasonic cleaning apparatus which includes an ultrasonic vibrating apparatus capable of attaining the above-described benefits. Depending upon the embodiment, one or more of these benefits may be achieved.

[0023] These and other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1A is a simplified sectional view showing an embodiment of an ultrasonic vibrating apparatus according to the present invention, which is taken along line B-B of FIG. 1B;

[0025]FIG. 1B is a simplified sectional view taken along line A-A of FIG. 1A;

[0026]FIG. 2A is a simplified sectional view showing an embodiment of an ultrasonic vibrating apparatus according to the present invention, which is taken along line C-C of FIG. 2B;

[0027]FIG. 2B is a simplified sectional view taken along line D-D of FIG. 2A;

[0028]FIG. 3 is a simplified side elevation view showing an embodiment of an ultrasonic cleaning apparatus according to the present invention;

[0029]FIG. 4 is a simplified view of the ultrasonic cleaning apparatus shown in FIG. 3 which is viewed from a right-hand side of FIG. 3;

[0030]FIG. 5 is a sectional view showing a conventional ultrasonic cleaning apparatus; and

[0031]FIG. 6 is a simplified side view diagram of an alternative embodiment of the present invention

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0032] According to the present invention, techniques for cleaning objects have been provided. More particularly, the invention provides an ultrasonic vibrating apparatus for cleaning an object to be cleaned using an ultrasonic wave and an ultrasonic cleaning apparatus having the same incorporated therein. Merely by way of example, the invention can be applied to cleaning semiconductor wafers. But it would be recognized that the invention can also be applied to masks, hard disks, flat panel, MEMS object, optical devices, and the like.

[0033] Now, the present invention will be described with reference to FIGS. 1A to 4 and 6.

[0034] Referring first to FIGS. 1A and 1B, an embodiment of an ultrasonic vibrating apparatus according to the present invention is illustrated. These figures are merely illustrations and should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. An ultrasonic vibrating apparatus of the illustrated embodiment which is generally designated at reference numeral 10 generally includes a box-like member 12 of which one end is open and the other end acts as a vibrating plate 11, a plate-like member 13 formed into a size larger than the one open end of the box-like member 12 and arranged so as to close the one open end of the box-like member 12, at least one ultrasonic transducer 15 fixedly mounted on an inner or upper surface of the vibrating plate 11 of the box-like member 12 by means of an adhesive 14 (or other means), and a cleaning liquid ejecting mechanism 16 acting as a bubble removing means for removing bubbles adhering to an outer or lower surface of the vibrating plate 11 or collecting in proximity to the outer surface of the vibrating plate 11 during cleaning of an object to be cleaned or a cleaned object. The vibrating plate 11 which openably closes an upper opening of a cleaning tank (not shown) in a cover-like manner and has the ultrasonic transducer 15 fixedly mounted thereon is so arranged that a vibrating surface thereof downwardly faces and is immersed in cleaning liquid stored in the cleaning tank.

[0035] The ultrasonic vibrating apparatus 10 of the illustrated embodiment is preferably constructed so as to be pivotally coupled to the cleaning tank by means of a hinge, to thereby openably close the upper opening of the cleaning tank. Additionally and/or alternatively, the ultrasonic vibrating apparatus 10 may be operatively associated with the cleaning tank by means of a vertically moving means such as a robot or the like, to thereby be selectively vertically moved with respect to the upper opening of the cleaning tank. Also, in order to permit the ultrasonic vibrating apparatus 10 to be applied to an existing cleaning tank, the plate-like member 13 may be provided with an adaptor for suitably or conformably mounting the apparatus 10 on the cleaning tank therethrough. Alternatively, the existing cleaning tank may be provided on a periphery thereof with a frame or the like for mounting the ultrasonic vibrating apparatus 10 on the cleaning tank therethrough.

[0036] The cleaning liquid ejecting mechanism 16 acting as the bubble removing means is arranged so as to keep bubbles from collecting in proximity to the vibrating plate 11 or adhering to the vibrating plate 11 during ultrasonic cleaning, to thereby prevent excessive heating of the ultrasonic transducer 15 due to a failure in cooling of the vibrating plate 11 by the cooling liquid. The cleaning liquid ejecting mechanism 16 is constituted by a cylindrical member of which both ends are closed and which has a cleaning liquid feed pipe 17 connected thereto. The cleaning liquid ejecting mechanism 16 is formed on a side wall thereof with a plurality of cleaning liquid ejecting ports 18 for ejecting the cleaning liquid therefrom toward the ultrasonic vibrating plate 11. The cleaning liquid ejecting mechanism 16 is fed with cleaning liquid 20 under a high pressure through the cleaning liquid feed pipe 17 from a cleaning liquid feed port 19 arranged so as to communicate with the cleaning liquid feed pipe 17. The cleaning liquid 20 is made so as to have the same composition as that stored in the cleaning tank. Then, the cleaning liquid ejecting mechanism 16 ejects the cleaning liquid 20 from the cleaning liquid ejecting ports 18 toward a location near the vibrating plate 11. This permits the cleaning liquid thus ejected to remove bubbles collecting in proximity to the vibrating plate 11 or adhering thereto.

[0037] The cleaning liquid ejecting mechanism 16 is mounted on the plate-like member 13 through the cleaning liquid feed pipe 17 arranged in proximity to one end of the cylindrical member and a fixing member (not shown) arranged in proximity to the other end thereof, to thereby effectively remove bubbles from a vicinity of the vibrating plate 11. A manner of fixing of the cleaning liquid ejecting mechanism 16 and a position thereof are not limited to the above, thus, they may be suitably selected otherwise. Also, arrangement of the cleaning liquid ejecting mechanism 16 acting as the bubble removing means may be eliminated as desired. In this instance, a period of time for which the ultrasonic transducer is operated is limited so as to prevent excessive heating of the ultrasonic transducer.

[0038] The vibrating plate 11 is made of a material which is resistant to the cleaning liquid. The material is selected from the group consisting of stainless steel such as SUS 304, SUS 316 or SUS 316L; tantalum; fused quartz and silicon carbide; and stainless steel of 1 μm (Rmax) in surface roughness. The material is subjected to fluoroplastic coating or passivation such as electropolishing or electroplating, or the like. Alternatively, the box-like member 12 as well as the vibrating plate 11 mounted on the lower surface of the vibrating plate 11 may be made of the above-described material. Also, the vibrating plate 11 may be formed to be suitably thick. When the plate is used as a vibrating plate of the resonance type, it may be formed with a thickness one half, one time, 3/2 times, twice, 5/2 times, 3 times, or greater or as large as a wavelength of an ultrasonic wave generated by ultrasonic vibration. Further, in the illustrated embodiment, a packing 23 which is resistant to the cleaning liquid is arranged between the box-like member 12 and the plate-like member 13 to prevent intrusion of the cleaning liquid or the like into the box-like member 12.

[0039] The ultrasonic transducer 15 may be constituted by any suitable conventional vibrator which generates an ultrasonic wave of any frequency within a range of between 200 kHz and 5 MHz. The vibrating plate 11 is fixedly mounted thereon with at least one ultrasonic transducer 15. In the illustrated embodiment, four such ultrasonic transducers 15 are arranged thereon. The ultrasonic transducers 15 each have a voltage at a predetermined level applied thereto from each of connectors 22 through each of lead wires 21. Each of the connectors 22 is provided at a portion thereof mounted on the plate-like member 13 with a suitable sealing means which prevents intrusion of the cleaning liquid or the like into the box-like member 12.

[0040] Referring now to FIGS. 2A and 2B, an alternative embodiment of an ultrasonic vibrating apparatus according to the present invention is illustrated. These figures are merely illustrations and should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. An ultrasonic vibrating apparatus of the illustrated embodiment which is generally designated at reference numeral 30 generally includes a box-like member 32 of which one end is open and the other end acts as a vibrating plate 31, a plate-like member 33 formed to have a size larger than the one open end of the box-like member 32 and arranged so as to close the one open end of the box-like member 32, and a wave transmission element 35 of which a lower end surface is fixed to an upper or inner surface of the vibrating plate 31 of the box-like member 32 by means of an adhesive 14 (or other means) and an upper end surface has at least one ultrasonic transducer 34 mounted thereon, resulting in guiding ultrasonic vibration therethrough. The ultrasonic vibrating apparatus 30 thus constructed is arranged so as to cover an upper opening of a cleaning tank (not shown). Also, the vibrating plate 31 which has the ultrasonic transducer 34 fixed thereon through the wave transmission element 35 by means of the adhesive 14 is so arranged that a vibrating surface thereof downwardly faces. The ultrasonic transducer 34 is fixedly mounted on the upper end surface of the wave transmission element 35. Thus, it will be noted that the ultrasonic vibrating apparatus 30 is constructed in substantially the same manner as the apparatus 10 described above, except that the ultrasonic transducer 34 and wave transmission element 35 are substituted for the ultrasonic transducer 15.

[0041] The wave transmission element 35 is formed thereon with a flange 36, which is mounted thereon with a cooling mechanism 37 for cooling the wave transmission element 35 and ultrasonic transducer 34 during generation of an ultrasonic wave. The cooling mechanism 37 is constituted by pipings connected between two through-holes 38 of the flange 36 of the wave transmission element 35, a cooling water inlet 39 a arranged outside the ultrasonic vibrating apparatus 30 and pipings connected between the through-holes 38 of the flange 36 and a cooling water outlet 39 b likewise arranged outside the apparatus 30. Thus, cooling water 39 c is introduced from the cooling water inlet 39 a to the cooling mechanism 37, fed via the through-holes 38 and then discharged from the cooling water outlet 39 c, during which the cooling water cools the wave transmission element 35 and ultrasonic transducer 34.

[0042] Any suitable element which has been conventionally known in the art may be applied to the wave transmission element 35 so long as it may be provided with such a cooling mechanism as described above and mounted on the ultrasonic vibrating apparatus 30. One of such conventional elements is typically disclosed in Japanese Patent Application Laid-Open Publication No. 94756/1998. A size of the wave transmission element 35 and the like may be selected as desired depending on the ultrasonic vibrating apparatus 30.

[0043] Application of the ultrasonic vibrating apparatus 30 to an existing cleaning tank, the box-like member 32 and the ultrasonic transducer 34 may be constructed in substantially the same manner as in the ultrasonic vibrating apparatus 10 of the embodiment described above. Also, the ultrasonic vibrating apparatus 30 may be provided with such a bubble removing means as described above with respect to the embodiment, to thereby remove bubbles adhering to the vibrating plate or collecting in proximity thereto.

[0044] As can be seen from the foregoing, the ultrasonic vibrating apparatus 10 and 30 may each be relatively readily applied to an existing cleaning tank, resulting in carrying out ultrasonic cleaning of a wafer or the like using an ultrasonic wave of a frequency within a range of between 200 kHz and 5 MHz, particularly, megahertz ultrasonic cleaning thereof using an ultrasonic wave of a frequency of between 500 kHz and 5 MHz. It is required that the cleaning conditions and the like be selected for every cleaning. Also, each of the ultrasonic vibrating apparatus 10 and 30, as described above, may be readily removed from the cleaning tank or pivotally moved about one end thereof with respect to the cleaning tank, so that maintenance and replacement of both ultrasonic vibrating apparatus and parts arranged therein such as the ultrasonic transducer and the like may be facilitated.

[0045] Referring now to FIGS. 3 and 4, an embodiment of an ultrasonic cleaning apparatus according to the present invention is illustrated. An ultrasonic cleaning apparatus of the illustrated embodiment which is generally designated at reference numeral 40 is generally constituted by a cleaning tank 42 having cleaning liquid in which cleaned objects 41 such as wafers or the like are immersed stored therein, as well as an ultrasonic vibrating apparatus 43. The ultrasonic vibrating apparatus 43 includes a box-like member 43 b of which one end is open and the other end acts as a vibrating plate 43 a, a plate-like member 43 c formed to have a size larger than the one open end of the box-like member 43 b and constructed so as to close the one open end of the member 43 b, at least one ultrasonic transducer (not shown) securely mounted on an inner surface of the vibrating member 43 a of the box-like member 43 b, and a bubble removing means 43 for removing bubbles adhering to the vibrating plate 43 a or collecting outside the vibrating plate during cleaning of the cleaned objects. The bubble removing means 43 may be constituted by, for example, a cleaning liquid ejecting mechanism. The ultrasonic vibrating apparatus 43 is arranged in proximity to an upper end of the cleaning tank 42 so that the vibrating plate 43 a of the box-like member 43 b may be immersed in the cleaning liquid stored in the cleaning tank 42.

[0046] Thus, the ultrasonic cleaning apparatus 40 of the illustrated embodiment includes the ultrasonic vibrating apparatus 43 constructed in substantially the same manner as the ultrasonic cleaning apparatus 10 described above and is arranged in proximity to the upper end of the cleaning liquid so as to permit the vibrating plate 43a of the box-like member 43b to be immersed in the cleaning liquid. Then, the ultrasonic cleaning apparatus emits an ultrasonic wave downwardly from above the cleaning liquid through the cleaning liquid to clean objects or wafers 41 immersed in the cleaning liquid. The wafers 41 may each be formed to have a size of, for example, 50.8 mm (2 inches), 101.6 mm (4 inches), 152.4 mm (6 inches), 203.2 mm (8 inches), 300 mm, 450mm or the like. The plate-like member 43 c may be so arranged that one end 44 thereof is hinged in proximity to the cleaning tank 42 so as to permit pivotal movement of the other end in a vertical direction. Alternatively and/or additionally, the other end of the plate-like member 43 may be vertically moved by any suitable vertically moving means such as a robot or the like.

[0047] In order to ensure such vertical movement of the plate member 43 c, the illustrated embodiment may be so constructed that the cleaning tank 42 is securely mounted on a base 46 a of a frame 46 by means of a fixing member 46 b and the plate-like member 43 c is hinged at the one end 44 thereof to columns 46 c mounted on the base 46 a, resulting in the plate-like member 43 c being pivotally moved about the one end. Also, the ultrasonic cleaning apparatus 40 may be provided with any suitable lock mechanism (not shown) so that the ultrasonic vibrating apparatus 43 may be kept fixed while keeping the vibrating plate 43 a immersed in the cleaning liquid. The lock mechanism may be configured so as to lock the other end 45 of the plate-like member 43 c opposite to the one end 44 thereof.

[0048] Also, the plate-like member 43 c may be mounted on the other end 45 thereof with a handle (not shown) to facilitate vertical movement of the other end 45 about the one end 44.

[0049] A configuration of the frame 46, a manner of fixing the cleaning tank 42, a manner of combining the ultrasonic vibrating apparatus 43 and the frame 46, and the like may be selected as desired.

[0050] The ultrasonic transducer (not shown), vibrating plate 43 a and the like incorporated in the ultrasonic vibrating apparatus 43 may be configured in substantially the same manner as those in the ultrasonic vibrating apparatus 10 described above.

[0051] The cleaning tank 42 is so constructed that an upper end 47 thereof is formed to have a rectangular shape, each side of which is corrugated so as to have a plurality of troughs 47 a. Also, the corrugation of each side of the upper end 47 of the cleaning tank 42 is so configured that the trough 47 a is positioned at each of comers 47 b of the rectangular upper end. Also, the cleaning tank 42 is equipped with an overflow tank 48 for receiving cleaning liquid overflowing the cleaning tank 42 therein. Further, the cleaning tank 42 is formed at a lower portion of a side wall thereof with a plurality of cleaning liquid ejecting ports (not shown) for ejecting cleaning liquid into the cleaning tank 42 from an outside thereof and a discharge port provided at a bottom wall thereof so as to discharge waste cleaning liquid from the cleaning tank 42. The cleaning tank 42 may be made of a material which is resistant to the cleaning liquid and is not fused due to ultrasonic vibration. The material may be selected from the group consisting of fused quarts, tantalum, stainless steel of 1 μm (Rmax) in surface roughness, silicon carbide, alumina, fluoroplastic or the like.

[0052] The cleaning tank 42 is provided on the sides of the upper end 47 thereof with the troughs 47 a, so that the cleaning liquid may uniformly overflow the upper end 47 of the tank 42 through the troughs 47 a.

[0053] The cleaning liquid is continuously or intermittently fed from the cleaning liquid ejecting ports to the cleaning tank 42, so that excessive or waste cleaning liquid may overflow the upper end 47 of the cleaning tank 42 and be guided to the overflow tank 48. The cleaning liquid ejecting ports may be constituted by a plurality of holes formed through a side wall of each of two cylindrical members 50 of which one end is closed and which are arranged in proximity to a lower side surface of the cleaning tank 42 to eject the cleaning liquid therefrom toward the wafers 41. Thus, cleaning liquid under a high pressure is injected through a feed port 50 b into the each of the cylindrical members 50 and ejected from the cleaning liquid ejecting ports into the cleaning tank 42.

[0054] The overflow tank 48, as shown in FIGS. 3 and 4, has a bottom wall obliquely formed, to thereby permit overflowing cleaning liquid to readily collect at a discharge port 48 a.

[0055] The cleaning tank 42 is provided therein with a wafer fixture 51 for holding the wafers 41. For this purpose, the wafer fixture is formed with a plurality of fit sections in each of which one of the wafers 41 is fittedly held at only a part thereof. A configuration of the wafer fixture, that of the fit sections and the like may be selected as desired. In FIGS. 3 and 4, reference character 43 e designates connectors for applying a voltage at a predetermined level to the ultrasonic transducers (not shown), 43 f is a cleaning liquid inlet and 52 is a packing which is resistant to the cleaning liquid. The packing 52 functions to prevent intrusion of the cleaning liquid into the ultrasonic vibrating apparatus 43.

[0056] In an alternative embodiment of an ultrasonic cleaning apparatus according to the present invention, an ultrasonic vibrating apparatus constructed in substantially the same manner as the ultrasonic vibrating apparatus 30 is substituted for the ultrasonic vibrating apparatus 43 incorporated in the ultrasonic cleaning apparatus 40 described above. Also, the ultrasonic vibrating apparatus is pivotally vertically moved about one end thereof as in FIG. 3. The remaining parts of the embodiment may be constructed in substantially the same manner as the embodiment described above with reference to FIGS. 3 and 4. Further, the ultrasonic cleaning apparatus of the alternative embodiment may include a cleaning liquid ejecting mechanism acting as a bubble removing means, as in the ultrasonic vibrating apparatus 10 described above.

[0057]FIG. 6 is a simplified side view diagram 70 of an alternative embodiment of the present invention. As shown, the diagram 70 includes a variety of similar features as those described above. The diagram includes an apparatus that has a bath region 83, which has an underlying bath dry area 85. A mounting frame 71 is also coupled to the bath region. A removable vibrating apparatus is coupled to the upper region of the bath. The removable vibrating apparatus has lower portion of lid 81, which couples to bath region. The lower portion includes a hinge device 75, which couples the lower portion of the lid to the upper portion of the lid 71. The upper portion of the lid also includes a handle 79, which allows a user to lift the upper lid about the hinge. The upper lid includes the vibrating apparatus such as the ones previously described, but can be others. According to this embodiment, a conventional bath can be fitted with upper and lower lid apparatus.

[0058] In each of the ultrasonic cleaning apparatus embodiments described above, the cleaning liquid ejecting mechanism acting as the bubble removing means may be arranged in the cleaning tank rather than the ultrasonic vibrating mechanism, to thereby eject the cleaning liquid stored in the cleaning tank toward the wafers.

[0059] As described above, in each of the ultrasonic cleaning apparatus embodiments described above, the wafers are subjected to ultrasonic cleaning while being kept immersed in the cleaning liquid. Also, the ultrasonic vibrating apparatus is arranged above the cleaning tank and readily upwardly moved from the cleaning liquid, to thereby facilitate maintenance and replacement of both ultrasonic vibrating apparatus and parts or members arranged therein such as the ultrasonic transducers and the like. The ultrasonic cleaning apparatus of each of the embodiments may be effectively applied to, in addition to a wafer, any other suitable objects such as liquid crystal and the like by selecting a suitable size for the cleaning tank, a frequency for the ultrasonic transducer, power for ultrasonic vibration and the like.

[0060] As can be seen from the foregoing, the ultrasonic vibrating apparatus and ultrasonic cleaning apparatus of the present invention each permit ultrasonic cleaning of a cleaned object such as, for example, megahertz ultrasonic cleaning thereof, to be carried out using an existing cleaning tank.

[0061] Also, the ultrasonic vibrating apparatus and ultrasonic cleaning apparatus of the present invention each attain cleaning of a cleaned object while keeping it immersed in cleaning liquid.

[0062] Further, the ultrasonic vibrating apparatus and ultrasonic cleaning apparatus of the present invention each facilitate maintenance and replacement of both ultrasonic vibrating apparatus and components arranged therein.

[0063] While preferred embodiments of the invention have been described with a certain degree of particularity with reference to the drawings, obvious modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. 

What is claimed is:
 1. A method for treating objects, the method comprising: applying a plurality of acoustic waves from an energy source to an upper portion of an object to be treated, the object being immersed in fluid, the fluid comprising liquid; and maintaining the acoustic waves from the upper portion of the object to a lower portion of the object such that the entire object is subjected to the acoustic waves, the object being substantially free from a shadowing influences for an other object in the fluid.
 2. The method of claim 1 wherein the acoustic waves comprise a frequency ranging from about 200 kHz to 5 Mhz.
 3. The method of claim 1 wherein the fluid comprises water and ammonium ions.
 4. The method of claim 1 wherein the fluid comprises an etchant, the etchant being selected from HF, HCl, and H₂SO₄.
 5. The method of claim 1 wherein the acoustic waves prevent a particle from reattaching itself onto a surface of the object, the particle having a dimension of less than 0.5 micron in size.
 6. The method of claim 1 further comprising directing fluid across a plate coupled to the energy source to generate a force that maintains the plate free from a possibility of accumulating a bubble.
 7. The method of claim 6 wherein the force is a flow.
 8. The method of claim 1 wherein the object is selected from a semiconductor wafer or a flat panel, a mask, a disk, or a MEMS object.
 9. The method of claim 8 wherein the semiconductor wafer is selected from a patterned wafer or a blank wafer.
 10. A system for treating objects, the system comprising: a vessel configured for holding a fluid comparing a liquid, the vessel comprising a lower portion and an upper portion; an acoustic vibrational source being configured to operate at 400 kHz to 5 MHz, the acoustic vibrational source being coupled to the upper portion of the vessel, the acoustic vibrational source having an active area that is substantially similar to a width of a substrate being treated, the active area providing acoustic waves along an entire width of the substrate being treated.
 11. The system of claim 10 wherein the acoustic vibrational source is mounted on a lid of the vessel.
 12. The system of claim 10 wherein the vessel is manufactured from quartz.
 13. The system of claim 10 wherein the acoustic vibrational source comprises a plurality of transducers, each of the transducers being capable of converting an electrical signal into a mechanical signal.
 14. The system of claim 10 wherein the lower portion of the vessel is formed to conform to a bottom region of the substrate to be treated.
 15. The system of claim 10 wherein the acoustic vibrational source comprises a plurality of transducers, each of the transducers being capable of converting an electrical signal into a mechanical signal through a plate, a portion of the plate being submerged in the liquid.
 16. The system of claim 10 wherein the acoustic vibrational source is sealed in a chamber, the chamber being maintained in an inert atmosphere.
 17. The system of claim 10 wherein the acoustic vibrational source is maintained under a positive pressure relative to an ambient pressure.
 18. The system of claim 10 wherein the acoustic vibrational source is mounted on a movable lid of the vessel.
 19. The system of claim 10 wherein the vessel comprises at least one sensor for detecting the fluid level such that a plate coupled to the acoustic vibrational source is maintained in the fluid.
 20. An ultrasonic vibrating apparatus for irradiating an ultrasonic wave to an object kept immersed in cleaning liquid stored in a cleaning tank formed with an upper opening, comprising: a vibrating plate for closing said upper opening of said cleaning tank in a lid-like manner; and at least one ultrasonic transducer fixedly mounted on said vibrating plate; said vibrating plate being arranged in such a manner that a vibrating surface thereof outwardly faces and is adapted to be immersed in the cleaning liquid stored in said cleaning tank.
 21. An ultrasonic vibrating apparatus for irradiating an ultrasonic wave to an object kept immersed in cleaning liquid stored in a cleaning tank formed with an upper opening comprising: a vibrating plate for closing said upper opening of said cleaning tank in a lid-like manner; a wave transmission element; at least one ultrasonic transducer fixedly mounted on said vibrating plate through said wave transmission element; and said vibrating plate being arranged in such a manner that a vibrating surface thereof outwardly faces and is adapted to be immersed in the cleaning liquid stored in said cleaning tank.
 22. An ultrasonic vibrating apparatus as defined in claim 20 or 21, wherein said vibrating plate is provided with a hinge and/or a vertically moving means, to thereby be operatively associated with said cleaning tank.
 23. An ultrasonic vibrating apparatus as defined in any one of claims 20 to 22, wherein a vibrational frequency of said vibrating plate is set to be within a range of between 200 kHz and 5 MHz.
 24. An ultrasonic vibrating apparatus as defined in any one of claims 20 to 23, wherein said vibrating plate is made of a material subjected to a treatment selected from fluoroplastic coating and passivation; said material being selected from the group consisting of stainless steel such as SUS 304, SUS 316 or SUS 316L; tantalum; fused quartz; silicon carbide; and stainless steel of 1 μm (Rmax) in surface roughness.
 25. An ultrasonic vibrating apparatus as defined in any one of claims 20 to 24, .further comprising a bubble removing means arranged on a lower surface of said vibrating plate so as to eject cleaning liquid of a composition identical to that of the cleaning liquid in said cleaning tank to remove bubbles adhering to the lower surface of said vibrating plate therefrom.
 26. An ultrasonic cleaning apparatus comprising: the ultrasonic vibrating apparatus defined in any one of claims 20 to 25; and a cleaning tank formed with an upper opening on which said ultrasonic vibrating apparatus is mounted.
 27. An ultrasonic cleaning apparatus comprising: the ultrasonic vibrating apparatus defined in any one of claims 20 to 25; a cleaning tank formed with an upper opening on which said ultrasonic vibrating apparatus is mounted; and a bubble removing means arranged in proximity to said upper opening of said cleaning tank and constructed so as to eject cleaning liquid of a composition identical to that of cleaning liquid stored in said cleaning tank to a lower surface of said vibrating plate of said ultrasonic vibrating apparatus, to thereby remove bubbles adhering to said lower surface of said vibrating plate therefrom. 